Improvement in iron bridges



I. B. EADS.

` Iron Bridges. y N0. l1-2,379. Patented'Septe-mbler2, .1873.

hummm L. H@ @EMS To all whomit may concern:

.Un-Irun STATES nfrnnfr FFICE.

JAMES B. EADS, OF ST. LOUIS, MISSOURI.

i.. IMPROVEMENT IN IRON BRIDGES.

Specification forming part of Letters Patent No. 142.379, dated September 2, 1873 5 application filed March 19, 1873.

Be it known that I, JAMES B. EADS, of the city and county of St. Louis and State'ot Missouri, have invented a certain Improvement in Bridges, of which the following is a specication:

My invention consists, in part, in the erection of arches by building them out from the piersfor abutments, from whence they are held up by guys from the tops or sides of the piers or abutments until they are joined in the center, and no longer need the said guys, and in such manner that the arches, when first formed, constitute only a small part of the finished arch, and serve, at first, only to sustain the additional members needed to give the power of bearing the maximum load intended by the completed structure. .My invention also enables me to construct the bridge without anyA scaffolding or centering beneath the arches, and with the use'of but little temporary Work of any description, as is more particularly described hereinafter. The guys which sustain the incipient arch may be, in part, formed of the horizontal members that constitute the girder. My invention also embodies a method of imparting the necessary expansive strain needed to force the two ends of the arch apart at the center, when they are first joined, so as to raise the curve of the arch to the normal position, and thus relieve the strainv on thevguys and enable the diagonal or slanting portion of said guys to be taken off when desired. The expansive sections are formed in two parts, arranged to be forced endwise to lengthen the sections either by a screw, by hydraulic pressure, or other convenient means. I

In the accompanying drawings, Figure 1 is ya side elevation of one-half of a bridge of the proposed construction. Fig. 2 is a transverse section through the crown of the arch, showing the position of the members of the arches. Fig. 3 shows, in axial section, one of the closing or center tube-sections expansible by hy# draulic pressure. Fig. 4 is an axial section of one of the closing-tubes, showing an expanding-screw to force the ends apart. Fig. 5 shows transverse sections of Fig. 4.

a a' represent straight tubular sections of the arches A A', joined together by collars at CASE B.

B, and the members of the arch connected by stays, struts, and braces C C' D, which may be arranged in any desired manner. E is the pier or abutment, e the skew-back, and F a tower or pillar extending upward from the springing of the arch. The tower F should be so constructed as to bear a horizontal strain. G are uprights connecting the arch A to the truss-girder l1. The girder H may have upper members h and lower members h', connected by stays and braces g. I I', 85e., are guys, whose purpose is to support the bridge while under construction. The guy I extends from the top of the tower F to the point i of the arch; and the guy I' also extends from the same point to the point 'i' of the arch, from which isl erected an upright, K, carrying a guy, I", extending to a point, fi", from which arises an upright, K', from whose` top extends a guy, 1"', and so on to, or near to, the middle of the arch. The uprights K K', 8vo., and the guy I I', Ste., may be formed in part by the girder H. The closing tube-sections are shown enlarged in Figs. 3, 4, and 5. They are represented with the barrelformed of a number of section-staves, Il, inclosed in a cylindrical sleeve, M; but I do not confine myself to this construction of tube. The tube-section is divided at N and the ends strengthened by re-enforcing rings O. l

In Fig. 3 the extension is done by a hydrostatic apparatus having a cylinder, P, and plunger, Q, secured each to one part of the tube. The water or other liquid is forced into the chamber R through a pipe, r, and its escape prevented by packing S.

In the form of expanding tube shown in Figs. 4 and 5 theinterior of the ends are screw-threaded atnwith right and lefthand screws,in which screws a tube, T, having key-holes t, by means of which it may be turned to extend the tubesection endwise. U are semi-cylindrical' pieces which are inserted between the ends N, after the tubes are extended, to take a part or all of the pressure after the removal of the guys and constitute part of the arch. V, in Figs. 4 and 5, are transverse bolts to hold the pieces U in position. The piecesUin Fig.3 may be screwed fast to the plunger Q.

In constructing the bridge, the piers E and towers F are first built, and the upper tubes of the arch, consisting of lengths a and joints B, are built out to t together with the girder. This point is then connected by guysI to the upward extension or top F of the pier. The said guys may pass over the top of the pier to a section of bridge similar to the part already described, and on the opposite side of the pier, so as to make a counterpoise or the guys may be carried over the pier to any fixed object to sustain the strain, provided the pier itself is not strong enough. After securing the guys I in position7 the tubes a and girdcr are built out to t" and guys carried from that point to.

the top of the tower F, and an upright, K, erected at i', and the girder and the tubes a are thus built out to the crown of the arch, the other end of the arch having been built out to the same point from the other pier or abutment. The expanding sections in their contracted condition are put in position between the two ends. Owing to the extension of the girder and guys, and the compressionv of the uprights and arch, and consequent depression of the crown, the two ends ofthe arch will be in too close proximity, and this is rectied by the endwise extension of the center tubes. After the extension-tubes are placed in position they are expanded, either by hydrostatic pressure or by turning the screw T, until the crown of the arch is raised to its proper position; or said tubes may be extended by wedges or other means.

The latter plans may be quite sufcient in small spans. The girder may now be completed, leaving the bridge with a girder and a single series of single tube ribs or arches, a a, one each side beneath the girder. After this the required number, of tubular arches are added to each completed arch, each section a being supported, when xed in position, by the completed arch already erected,

` and as each course of sections of new tubes is finished from abutment to abutment, one each side of the girder, they are expanded by their expansion-tubes to bring' them into mutual support of the structure with those before completed. Thus, the rst arches or series of sections need only be of strength sufficient to sustain themselves, the second course of sections, and the girder, so that series after series of arches may thus be put in place, and, by means of their respective extension-tubes, expanded to the proper degree to distribute the strain due to the weight of the bridge and load equally on each system of arches until the strength desired will be attained. The girder may likewise be completed from tower to tower, so light as to simply possess sufficient strength to hold the arches in form while they are building, and afterward it may receive additional members in its various parts to give it the additional strength needed for the finished bridge.

It will thus be seen that it is quite possible to span very wide rivers or chasms with incipient structures of great lightness, but which may finally he strengthened to any requisite degree. l

The joints which connect the sections must be arranged under each other, or at the points where the vertical connections with' the girder are made. Of course, the sections of the arches can be tubular or of any desired form, and the girder may be of plate, lattice, or other form, and made to resist tensile and compressive strains in each chord.

The girder may be made of strength only sufficient at first to hold its own weight safely two panels beyond a strut, g, and the weight of the struts and extended section of arch. The extended ends, being secured to the struts, and these to the girder, will thus be sustained until the guys are put on, as shown.

I do not limit my claim'to the use of the expansion-tubes to arches of the construction described. They are applicable in ribbed arches, or those with spandrel bracing, and may be used at the abutments or in any part of the arch advantageously in erecting long spans. Nor do I limit my claim to the method of erection by forming a skeleton span of a trussed arch, as described, for it can be applied advantageously in the erection of all kinds of arched bridges, and even of longspan trusses. The explanation of using it in a trussed arch, as described, will enable skillful engineers to apply the same system in other forms (arches or trusses) of long spans.

I claim herein as new and ofmy inventionl. The construction of a complete skeleton span of a trussed arch, constituting a part of the proposed bridge, when the arch and truss are built out together from the piers and abutments, substantially as described, to form the support for the remaining arches and trusses of the span.

2. The combination of expanding voussoirs with the arches of bridges, substantially as described, for the purpose of bringing such arches to their proper height, and to enable each arch in a lateral series composing a span to be extended to its proper length, which will insure its bearing its contemplated sha-re of the load.

JAS. B. EADS.

Witnesses:

SAML. KNIGHT, GEO. C. FABIAN. 

